1. Field of the Invention
The instant invention relates to a stationary, cooled turbine vane having improved means for cooling the interior and exterior of the vane.
2. Brief Description of the Prior Art
Stationary vanes in turbine engines are typically located directly adjacent the outlet of the combustion chambers and are subject to very rigorous operating conditions. They are exposed to extremely high temperatures, repeated thermal shocks upon each change in operating condition and non-uniformities in the temperature that effect different zones of the vane (leading edge, concave face, convex face and trailing edge) to bring about internal stresses which accelerate the fatigue of the vane structure.
Cooling of the stationary turbine vanes is known and is generally accomplished by the circulation of air taken from the turbine compressor and directed onto the interior or exterior surfaces of the vanes. Air directed to the interior of the hollow vanes may exit through a plurality of cooling holes through the vane wall to form a protective cooling film along the exterior surfaces of the vane. The primary purpose of such cooling is to limit the maximum temperature reach by the vane material and to minimize the temperature gradient existing on different zones of the vane in order to reduce thermal stresses. At the same time, the cooling air taken from the compressor must be kept to a minimum in order to minimize the loss of efficiency of the compressor.
Various arrangements for promoting heat exchange between different zones of the vanes are known, such as the provision of studs, bridges, fins and flow spoilers inside the hollow vane cavity. An arrangement of this type is described in Franch patent 2,473,621. It is also known to provide a heat sink of a body of porous material in the interior of the vane such that it occupies all or a portion of the cavity. An example of such a porous body formed of metal shavings bound together by diffusion brazing is shown in U.S. Pat. No. 4,440,834 to Aubert et al. Although these known arrangements have proven generally satisfactory, they have not provided sufficient cooling of the vanes under all operating conditions.